1. Field
The present disclosure relates to preparation of alcohol by culturing alcohol-producing microorganisms in a waste fermented solution remaining after distilling ethanol in the process of producing bioethanol.
2. Description of the Related Art
Due to high oil prices and concerns on global warming resulting from the use of fossil fuel, biofuel production is increasing rapidly globally. Especially, the production of bioethanol, which is commercially available by fermentation, has increased steeply. In the US, Brazil, Canada and Sweden, bioethanol is used as automobile fuel. Also, China, Australia and Japan are actively introducing and expanding the use of bioethanol. As for Korea, researches and developments have been made on bioethanol since 1988 with the enactment of the “Alternative Energy Development Promotion Act”. The conclusion is that bioethanol may be safely mixed with gasoline in an amount of 3-5%.
Since waste fermented solution is generated in an amount as much as 20 times the produced ethanol from the bioethanol-producing plants, an effective treatment thereof is required. Usually, the waste fermented solution is processed as follows. It is concentrated after centrifugation, or mixed with solid materials and then dried to make animal feed. Some of the waste fermented solution is used to dilute the source material, and the remainder is treated by methane fermentation. There has been no attempt to produce butanol using the waste fermented solution as yet.
Glycerol is one of the fermentation products by yeast. 3-5.3 g of glycerol is produced from 100 g of glucose. Since the ethanol waste fermented solution contains glycerol as well as many other byproducts such as lactic acid, acetic acid, ethanol, etc., an effective treatment of the waste fermented solution using them will be necessary.